CHICAGO— Every year, thousands of spills release crude oil into the ocean. Some spills are tiny. Others can be huge. A new study now finds that wherever it occurs, that oil pollution may harm fish. In new tests, oil impaired the activity of structures in the cells of fish hearts. Those changes crippled the organized pitter-patter of an animal’s heartbeats.

Researchers already knew that oil pollution harms heart health in hatchlings and in embryonic fish (those still in eggs). What they didn’t understand was precisely how oil did that.

To find out, marine scientist Barbara Block of Stanford University in Palo Alto, Calif., and her co-workers scooped up some of the oil floating in the Gulf of Mexico. It had been released during the 2010 Deepwater Horizon spill. They added tiny amounts of this oil to cells from the hearts of bluefin and yellowfin tuna. Those isolated cells were growing in a dish.

The oil triggered the cells to behave in an irregular and clashing pattern. In a whole fish, irregular heartbeats can prove fatal.

Block’s team identified a second problem as well. Tiny electrical discharges regulate the beating of heart cells. A system of potassium and calcium ion channels in the cells normally pace those electrical signals. These channels help heart cells create electrical jolts that coordinate the individual cells. When this works, the cells will beat in sync. But after exposure to the oil, the pacing of those electrical signals went haywire.

Crude oil consists of a mix of dozens if not hundreds of different types of chemicals. They’re known as hydrocarbons. The researchers now suspect that hydrocarbons in the oil may essentially gum up those ion channels. Block’s team reported its new findings February 13 in Chicago at the annual meeting of the American Association for the Advancement of Science. A report showing details of their tests appears in the February 14 Science.

The new data may even have implications for people. Indeed, the authors note, the newly seen effects on ion channels may explain why hydrocarbon pollutants in the air have been linked to irregular heartbeats in people.

Power Words

crude oil Petroleum in the form that it comes out of the ground.

embryo A vertebrate, or animal with a backbone, in its early stages of development. As an adjective, the term is embryonic.

hatchling A young animal that recently emerged from its egg.

hydrocarbon Any of a range of large molecules created by chemically bound carbon and hydrogen atoms. Crude oil, for example, is a naturally occurring mix of many hydrocarbons.

ion An atom or molecule with an electric charge due to the loss or gain of one or more electrons.